The result was you considered more what prize money was given. So the Normal Series was a pretty good deal, even though it was somewhat long. And the Mega-Speed was reckoned to be the most time-wise efficient.
The LM-giving series (XXvsYY) weren't particularly lucrative, but, true, did pay enough for quite a lot of mods, and were for a long time very engaging--something about them all being similar, and yet different, somehow. The GTC also gave an LM car, and was the only non-LM event to award an LM car (although many LM events could be won with non-LM cars; some easily).
(Excepting the Nismo GT-R LM from the All-Night II which really wasn't an LM car).
Alright, properly I should make a distinction between just race-modified (e.g. XXvsYY), and proper LM events (GT-I and two enduroes only--and those common fields also included race-modifieds). I.e. perhaps I should distinguish between normal, LM and RM, not just normal and LM.
Of course, the XXvsYY were engaging for (what seemed at that time) a long time, because getting the license for the rest of the events was too difficult, as was the Normal where you couldn't cheat, er, I mean modify your cars.